The present invention relates to an anchor and anchor chain monitoring device for anchored floating objects, in particular ships.
During a ship""s voyage, monitoring devices are called into service to determine force acting on a securing mooring apparatus either in a harbor or on a floating buoy apparatus and, whenever necessary, should this force exceed a predetermined value, to trigger an appropriate measure in order to prevent the securing apparatus from renting and the respective floating vessel from then being carried unchecked into the waterway.
A method and a device for monitoring the force acting on a mooring hawser of a single-point mooring device during loading and unloading of a ship is known from DE-AS 21 34 104. According to this known method, the bow of the ship is fastened to the single-point mooring device via the mooring hawser in such a manner that the ship can swing freely and unhindered about the mooring hawser. In this state, the force acting on the mooring hawser is measured and transformed into a signal which is a gauge of the measured force acting on said hawser and which then is transmitted from the single point mooring device onto land or to the ship. The mooring hawser between the ship and the single point mooring device is then released as soon as the transmitted signal displays that force acting on the hawser exceeds a predetermined upper threshold value.
DE-GM-73 16 102 discloses an anchoring apparatus for a floating vessel utilizing a point-anchoring system with a plurality of hawsers. A monitoring means is provided having a monitoring station for receiving and displaying the signals from a plurality of stress meters in order to measure the mechanical stress in the hawser. An interim piece between the hawser securing section and a securing base member is disposed with a stress meter for this purpose.
A dynamic anchoring of ships and similar floating objects is known from DE-OS-2 410 528 in which a propelling means is provided and the ship on the surface of the water is anchored perpendicular to a first fixed point on the sea bed. A buoy, provided with its own dynamic anchoring means, is anchored at a distance from the ship such that no machine or apparatus located either on the ship or on said first sea bed fixed point can interfere with said dynamic anchoring means and the buoy in this manner is able to attain a fixed position with reference to a second point on the sea bed. With help of a measuring device located on the surface, working in concert with a ship""s course determining device, the relative position of the ship with respect to buoy and course is determined. Any deviation in position of the ship with respect to the first given sea bed point is corrected by an anchoring means operation respective to delivered error signals of the measuring device.
DE-OS-2 410 528 further describes a buoy encompassing dynamic anchoring means as well as electromagnetic signal transmitter and reflector means.
A method for positioning a watercraft is known from DE-OS-25 02 020 with which a ship is always kept within an outer circle corresponding to the largest permissible inclination of a drilling mud return pipe, a riser, respectively. To this purpose, an anchoring arrangement is employed, as is a plurality of computer-controlled propellers with blades pivotal about a vertical axis. The computer only actuates the propellers after the resultant of the external force acting on the ship or the riser tube angle of inclination exceeds a certain predetermined value.
When values of external force or riser tube angle of inclination remain under the predetermined threshold value, only the compensating by the anchoring arrangement itself serves to keep the ship within a smaller inner circle which has a smaller radius than the radius of the outer circle.
A shear pin for retaining means is known from DE-GM-77 15 093, in particular for mooring arrangements, having sectionally decremental reductions at a measuring point. Stress sensors are arranged in an axle bore of the shear pin; their cavity filled with an sealing compound which hardens subsequent to introduction. The stress sensors are comprised of strain gages which are arranged in pairs at the measuring point and connected via conduits to an electrical circuit.
Cable works with a core are known from DE-OS-27 48 922, in particular for mooring of ships. The core consists of a cable connectable to an indicator system by at least two cable wires. Coexistent its mechanical connection, the cable works also has a clutch which serves for non-contact switching of the cable, whereby one coupling half is arranged at the cable works end and the other half is arranged at a distance thereto. In both coupling halves, moreover, an engageable locking and securing agent is provided. The coupling half disposed at the cable works end has a read contact under its front end at which the cable end is connected; under the front end of the other coupling half, a permanent magnet is disposed which works in concert with the read contact.
A monitoring or alarm system for ship anchor chains is known from GB 2 265 468 A in which a stress sensor controlled by a control means continually measures the tension in an anchor chain. The momentary measured anchor chain tension is compared with a predetermined tension or with the maximum measured tension recorded during the current anchored period, and the control means emits a warning signal when the anchor chain tension is higher than a predetermined critical value. Transmission of the signals between the sensor and the control means can ensue via a cable connection as well as through propagation of electromagnetic waves.
From U.S. Pat. No. 3,823,395, a means for monitoring the payload on cranes and similar contrivances is known. Said means can determine the weight load. A transmitter allocated to the sensor transmits the measured signal to a receiver which in turn shows the signal on a display.
U.S. Pat. No. 4,912,464 discloses an anchor warning device for ships in which a motion detector is arranged on the anchor of a ship and which emits an alarm signal upon significant movement of a sunk anchor.
From U.S. Pat. No. 5,086,651, a device and a method for measuring the mechanical strain in a structural member is known. A material is employed which undergoes a change in phase when strained so that the mechanical strain of a system can be determined through a measurement of the phase change. To effect an even more precise determination, a plurality of elements may be arranged for the monitoring of a complex system, each of said elements formed respectively from one material.
EP-A-0 242 115 defines a method and a system for determining position on a moving platform, for example a ship, utilizing signals from GPS satellites. In this known method, the satellite signals received directly at the moving platform are compared with satellite signals received indirectly through interposing from a base station, thereby determining the momentary position of the moving platform.
The problematic nature of anchors for floating objects will first be described using the example of an anchored ship.
To anchor, a ship lowers an anchor hanging on an anchor chain or hawser onto the waterway bottom so that the anchor, as well as also a large portion of the anchor chain/hawser lies on the sea bottom. What is important here is that the fixation of the ship at a certain area is not effected through the anchor connecting with the sea floor, but rather through the weight imposed on the portion of the anchor chain/hawser lying on the sea floor.
An anchored ship thus can, within a certain given range, move freely about the leverage point of the anchor chain/hawser on the sea bottom biasing the ship, thereby allowing for some give against external forces acting on the ship, as for example the force of currents or winds. As the amount of such external forces acting on the ship increase, this may led to the reaching of a particular condition, dependent upon a value based on weight and the length of the anchor chain/hawser, in which the anchor chain/hawser no longer lies on the sea bed and a force or motion is exerted directly from the ship to the anchor over the anchor chain/hawser. The ship either then drags the anchor unchecked behind itself or, should the anchor be firmly hooked on the waterway bottom, can give rise to the anchor chain breaking or the anchor itself fracturing so that the ship then flounders unchecked and uncontrolled in the waterway and could possibly even run aground.
A situation of this sort is of course extremely dangerous, in particular when the wind direction is towards shore, or when the ship is located in an area having reefs, or when there are other potential shipping channel collision spots in the near vicinity.
Accordingly, it is the task of the present invention to provide an anchor chain, anchor motion and anchor force monitoring device which increases the level of safety for an anchored floating contrivance.
The principle of the present invention consists of recognizing an exceptional condition at a localized position on the anchor chain/hawser, on the anchor itself respectively, so as not to endanger the stability of the anchoring, measuring the force or motion exerted and wirelessly transmitting the measurement.
The device according to the present invention is disposed with a measuring means constituting at least one sensor, which is preferably integrated at the connection between the anchor and chain/hawser, or also at another section of the chain/hawser, or even on the anchor itself, or is mountable on the anchor. It should be emphasized that this type of measuring means can be configured in such a manner that a part of the means is disposed at a section of the anchor or the anchor chain/hawser, meaning under water, and another part of said measuring means is disposed in or on the floating contrivance or ship. It is also possible to allocate a part of the monitoring device independent of the floating contrivance and the anchor device when, for example, the anchoring of a floating contrivance is to be monitored from a ship or from land.
Correspondingly, the alarm device may be disposed on the floating contrivance itself or at another position on another floating object or at a position on land, etc.
Reference to the transition junction is to be understood as not only the point of connection between the anchor and the anchor chain/hawser, but likewise the area adjoining the anchor chain/hawser. What is significant is that the anchor and chain monitoring device should be at least partially disposed in the section which regularly lies on the sea bottom for the purpose of stable anchoring and which essentially renders no large conditional changes.
In a preferred embodiment of the anchor and chain monitoring device according to the present invention, a plurality of sensors are distributed over the anchor chain/hawser so that a localized condition of the anchor device can be determined.
It is also preferable that at least one sensor is either integrated into or disposed on the anchor itself.
The sensor preferably comprises a piezoelectric, resistive, capacitive or inductive sensor element.
The linking of the sensor, respectively the corresponding parts of the measuring means, and the remaining parts of the measuring means, respectively alarm device, can ensue via an electrical cable. In this instance, the cable is arranged parallel to the anchor chain and anchor cable or integrated into the anchor chain and/or anchor cable. This configuration, however, does have the disadvantage that the cable connection may become damaged.
According to a preferred embodiment, the transmission between the measuring means, respectively the parts of the measuring means disposed in the anchor chain/hawser or the anchor, and the parts of the monitoring device situated above water in the floating contrivance, etc., takes place in a wireless fashion, namely through ultrasound, infrared radiation, electromagnetic waves or other suitable wireless transmission methods of propagation.
This method has the fundamental advantage that it excludes the possibility of a cable connection being damaged during lowering and raising of the anchor.
The disadvantage of this configuration however is that interference may arise in circumstances of several floating contrivances being anchored near one another, namely that a ship may receive signals from anchor or anchor chain monitoring devices which actually belong to other vessels.
According to a preferred embodiment of the present invention, it is therefore recommended that when employing wireless transmission, a corresponding identification code be transmitted at the same time which uniquely identifies the transmitting device. Employing an appropriately equipped identification code, for example a digital numeral with a relatively high number of bits, ensures that randomly received signals are not identified as actual measurement results, which otherwise might lead to the triggering of a false alarm.
Instead of an identification made by means of an identification code or a particular identifying pattern, it is also possible to accordingly set the devices at differing frequencies so that the danger of reciprocal interference is reduced.
In a preferred embodiment of the anchor or anchor chain monitoring device according to the present invention, the transmitting means is provided with a control means which induces that the signals are transmitted at intervals, as well as a signal generating means which generates an identification signal which is characteristic for the individual transmission means and which uniquely identifies same, the control means inducing said identification signal to be transmitted at least once during each transmission interval; the alarm output means has a memory in which an identification comparison signal corresponding to each individual transmitting means is stored, as well as a comparison means which analyzes whether the identification signal emitted from the transmitting means concurs with the stored identification comparison signal in the alarm output means; and a forwarding or further processing of the signals received by the alarm output means only occurs when the signals received by the alarm output means and the stored identification comparison signals in the alarm output means are identical.
The anchor or anchor chain monitoring device according to the present invention consists of a transmitting means and a separate alarm output means. This configuration has the advantage that the alarm output means, which is usually directly combined with an actuator, for example a warning light or a siren, can be disposed in the range of vision and/or hearing of the user on board a ship or on land.
The alarm output means may also portably accompany or be worn by the user in any manner. An example hereto would be the user wearing the alarm output means similar to a watch on his wrist.
According to a preferred embodiment, the transmission of the data and identification signal transpires as a digital transmission. This ensures realizing a high data transmission reliability and, as this signal is composed of an accordingly high number of single bits, additionally enables selecting from among a large number of identification patterns.
It is possible at as early a stage as its manufacturing, to delegate a particular transmitting member to a particular alarm output member and vice-versa. However, this would have the disadvantage that, for example upon failure of the alarm output member, the respective transmitting member would likewise be rendered unusable and vice-versa.
According to a preferred embodiment, it is therefore recommended that the allocation between the transmitting member and the alarm output member be configured so as to be variable.
It is preferable in this case that the transmitting member and its respectively utilized alarm output member be employed in an identification signal change mode which enables the alarm output member to record and store the identification signal of its allocated transmitting member. According to a preferred embodiment, this allocation or paired mode comprises several tiers of security in order to prevent an unintentional and erroneous allocation of transmitting member and alarm output member.
The possibility of freely allocating transmitting members and alarm output members has considerable advantages in practical use. Should the alarm output member or the transmitting member fail, only the one defective device has to be replaced, not both. The remaining device can continue in its operation.
This variable allocation has the further advantage that a transmitting device may also be allocated two alarm output devices and vice-versa. It is then possible, for example, that a coastal station can make use of two alarm output devices for the purpose of monitoring the anchored positions of two ships.
Finally, it is also conceivable, particularly with respect to the alarm output means which can be correlated with other functions, that the user can employ disparate equipment models without having to obtain a new transmitting member each time.
In addition, the variable allocation allows for a fundamentally simplified manufacture of the monitoring device.
The identification signal change mode is preferably triggered by a manual actuating of the transmitting means to induce the transmission of a particular signal, the identification control signal, which indicates to the alarm output device that an allocation process should transpire. In order to avoid an unintentional allocation of several alarm output devices to one transmitting device, corresponding security measures can be provided at the alarm output device.
The actual allocation transpires in that, along with the identification control signal, the identification signal of the transmitting member is also emitted. The alarm output device, having been brought into identification signal change mode, receives this identification signal and stores it in the corresponding memory until that point in time when, in the course of a new allocation, a different identification signal is received.
According to a preferred embodiment of the present invention, computing means are installed either in the transmitting device or in the alarm output device.
This allows the anchor or anchor chain monitoring device user to receive an indication of the current condition of both the anchor and the anchor chain/hawser and furthermore, for example, its temporal or localized course of development.
Particularly preferred when employing radio signals is the utilization of signals in the long-wave range, meaning the utilization of radio signals having a frequency from 5 hertz to 100 kilohertz.
Studies have shown that a frequency range of 5 hertz to 50 kilohertz is particularly opportune for transmitting electromagnetic signals under water.
Both the transmitting as well as the alarm output member may be disposed so as to actuate additional functions.
One such additional function is the logging of signals from other sensors. This could be, for example, an entry indicator means constituting mechanical sensors on doors, windows and holds, or a motion sensor for recording movements, especially in a ship""s interior, a listing sensor to measure any pronounced tilt of the floating object, or even a flood sensor which indicates when bilge water level has exceeded a predetermined critical value. Furthermore, one or several sensors may be provided which measure the retaining strength of the mooring lines mooring a ship in a harbor. The central alarm means pools these signals and issues a warning alarm when one of the recorded measurements reaches a critical condition. This is usually the case when a predetermined critical threshold value of force or motion is exceeded.
When using sensors on mooring lines, a critical condition can also be reached when several mooring lines are used and none of these lines indicates a signal of force.
In the case of an alarm means which encompasses sensor signals only in connection with an anchor, as well as in the case of a central signal means which logs several sensors in the manner as described above, the warning signal can also be sent in a wireless transmission to the receiving device, for example which is carried by an onshore user. The user is then automatically informed about the critical condition of his ship.
The wireless transmission may transpire with the radio transmission technologies known for the radio range released for these frequencies. It may also be alternatively provided that the central alarm means is dialed up via a suitable modem of a portable telephone, for example a mobile telephone according to the GSM standard.
In all the foregoing wireless transmission methods mentioned, messages from a central alarms means to a remotely situated user can be transmitted acoustically or as an alphanumerical signal. In the former method, for example, after establishing a connection, per telephone for instance, text stored in the alarm means is played back acoustically such as, for example, the phrase xe2x80x9cwater on board.xe2x80x9d Or this text could be shown visually on the receiver""s display. It should be pointed out that the above-mentioned central device may also then be employed when no anchor chain monitoring device is activated, for example when the ship is just moored with lines in the harbor, or when just a line monitoring device is provided.
The invention furthermore provides a sensor for anchor chain monitoring which is not only especially opportune for use in the anchor chain monitoring device as described herewithin, but which can also be employed in monitoring devices having other characteristics than as described in claim 1. Said anchor chain sensor consists of an essentially cylindrical ring made of a piezoelectrically acting ceramic connected on both sides to metal disks which have an outer diameter corresponding to the outer diameter of the piezoelectric rings.
The metal disks are reciprocally linked to the anchor chain and/or the anchor such that a tension acting on the anchor chain and/or the anchor leads to a compressing of the ring.
The entire sensor is wholly cast into a waterproof sealing compound of plastic or similar material. Furthermore, the transmitter is also preferably affixed to one of said metal disks and is likewise situated within the protective sealing compound.
By means of such a device, a very strong signal can be generated when the corresponding stress is determined on the anchor cable, the sensor respectively.
In this configuration, the transmitting means remains in a stand-by mode during normal operation, using only very little energy. As soon as stress is effected on the sensor, a signal is generated by the piezo ring and fed to the transmitting means. This signal is what induces the transmitting means to switch to an actual operational mode.
This embodiment encompasses two possibilities for operational mode.
In the first possibility, the stand-by mode and the operational mode are coordinated such that switching to the operational mode only occurs when the signal registers above a control value signifying a critical load. In this embodiment, a warning signal is therefore emitted directly after switching from stand-by mode to operational mode. Or, to put it another way, as soon as a jerk which exceeds a predetermined measure is exerted on the anchor, the anchor chain respectively, the transmitter switches on and an alarm is triggered.
In a second embodiment, upon exceeding of a predetermined force on a sensor, a monitoring device provided with such a sensor is merely induced to switch from stand-by mode to operational mode. Then the device, in operational mode, takes a measurement of the force as previously described and as soon as the force exceeds a predetermined threshold, triggers an alarm.